Re: [PATCH bpf-next 2/3] bpf: Show precise rejected function when attaching to __btf_id functions

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Thu, Jul 10, 2025 at 9:27 AM KaFai Wan <mannkafai@gmail.com> wrote:
>
> Show the precise rejected function name when attaching tracing to
> __btf_id functions.
>
> $ ./fentry
> libbpf: prog 'migrate_disable': BPF program load failed: -EINVAL
> libbpf: prog 'migrate_disable': -- BEGIN PROG LOAD LOG --
> Attaching tracing to __btf_id function 'migrate_disable' is rejected.
>
> Signed-off-by: KaFai Wan <mannkafai@gmail.com>
> ---
>  kernel/bpf/verifier.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 275d82fb1a1a..2779d63e1f8b 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -23938,6 +23938,8 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
>                         return ret;
>         } else if (prog->type == BPF_PROG_TYPE_TRACING &&
>                    btf_id_set_contains(&btf_id_deny, btf_id)) {
> +               verbose(env, "Attaching tracing to __btf_id function '%s' is rejected.\n",
> +                       tgt_info.tgt_name);

"Attaching tracing to __btf_id" ?! What does it mean?
Drop "__btf_id" and "tracing" bits.

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